1. Field of the Invention
The present invention relates to a robot system which can be used to convey stacked objects.
2. Description of the Related Art
Known in the art is a robot system which successively conveys carton boxes and other stacked objects by a robot. The robot is provided at the tip end of an arm with a gripping device which grips an object and is configured so as to convey an object which is gripped by the gripping device to a target site situated at a separate location for subsequent processes.
In an existing robot system, a placement process is performed by operating a robot according to a command position prepared in advance so that the bottom surface of the object is flush with the surface of the target site. However, when the actual dimensions of the object differ from the expected dimensions, the object is not suitably positioned and as a result, excessive pushing force may be applied on the object or the object may fall off.
Another existing robot system is provided with a sensor which detects contact of the object with the target site and designed to release the object when the object contacts the target site. However, in such a robot system, an object has to be moved at a low speed from a position sufficiently far away from the target site toward the target site. Therefore, the conveyance efficiency is decreased.
Known various robot systems are configured to acquire position information of the stacked objects by sensors and perform a conveyance process (see Japanese Patent Publication Nos. 2010-005769, H07-053054, H07-299782, 2001-317911, 2013-154457, 2012-192490, and 2011-247819).
With the existing robot systems, it has been difficult to suitably perform the conveyance process when the three-dimensional shapes and dimensions of the objects are unknown or when there are substantial differences between individual objects. Therefore, there is a need for a robot system which is able to suitably perform a conveyance process even if the three-dimensional shapes or dimensions of objects are unknown.